CODEWITHSUNDEEP
rdplyr
Will Park
Will Park

Reputation: 75

Changing Column Names Except For The First Two Columns

I am trying to change column names using colnames() function in R, but I want to keep the first two column names unchanged. For instance,

    x <- c("A", "B", "C")
    x2 <- c( "D", "E", "F")
    ch <- c("G", "H", "I")
    ch2 <- c("J", "K", "L")
    ch3 <- c("M", "N", "O")

    df <- data.frame(x, x2, ch, ch2, ch3)

   x  x2  ch  ch2 ch3
1  A   D   G   J   M
2  B   E   H   K   N
3  C   F   I   L   O

I just want to add "x_" in front of these columns so I would use

colnames(df) <- paste("x", colnames(df), sep = "_")

which will change their names to

   x_x  x_x2  x_ch  x_ch2 x_ch3
1   A     D     G     J     M
2   B     E     H     K     N
3   C     F     I     L     O

with all the column names changed, which is not what I want to do. How can I keep the first two column names unchanged while changing rest of the column names? I've tried various different ways but so far I can only keep the first two column names unchanged and the rest column names erased. If it's possible, I would like to use only dpylr or just basic R. Thank you in advance!

Upvotes: 1

Views: 2959

Answers (5)

Jilber Urbina
Jilber Urbina

Reputation: 61204

Another alternative in R base: sub

> names(df) <- sub("(^ch.*)","x_\\1", names(df))
> df
  x x2 x_ch x_ch2 x_ch3
1 A  D    G     J     M
2 B  E    H     K     N
3 C  F    I     L     O

Upvotes: 1

moodymudskipper
moodymudskipper

Reputation: 47330

In base R:

i <- startsWith(names(df),"ch")
names(df)[i] <- paste0("x_",names(df)[i])
#   x x2 x_ch x_ch2 x_ch3
# 1 A  D    G     J     M
# 2 B  E    H     K     N
# 3 C  F    I     L     O

Upvotes: 1

akrun
akrun

Reputation: 887521

We could use rename_at from dplyr

library(dplyr)
df %>% 
   rename_at(vars(matches("ch")), ~ paste0("x_", .))
#  x x2 x_ch x_ch2 x_ch3
#1 A  D    G     J     M
#2 B  E    H     K     N
#3 C  F    I     L     O

Upvotes: 4

warner_sc
warner_sc

Reputation: 848

Specify the starting column number to add the string:

x <- c("A", "B", "C")
x2 <- c( "D", "E", "F")
ch <- c("G", "H", "I")
ch2 <- c("J", "K", "L")
ch3 <- c("M", "N", "O")

df <- data.frame(x, x2, ch, ch2, ch3)

colnames(df)[3:ncol(df)] <- paste("x", colnames(df[3:ncol(df)]), sep = "_")

df

Upvotes: 1

Punintended
Punintended

Reputation: 737

Rather than apply that function to all colnames, use [] notation to apply it to a subset of columns

colnames(df)[3:ncol(df)] <- paste("x", colnames(df)[3:ncol(df)], sep = "_")

And welcome to StackOverflow!

Upvotes: 2

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